WASHINGTON — President Obama used the 50th anniversary of the Voting Rights Act on Thursday to urge Congress to restore key elements of the law, arguing that court decisions and state statutes that discourage “certain kinds of folks” from voting are threatening to erode the fundamental promise of the civil rights-era bulwark.

A half-century after the measure outlawed practices that barred blacks or other minorities from voting, Mr. Obama said the nation had “conceptually” rejected discrimination in balloting, a mark of “huge progress.”

But, he said, “In practice, we’ve still got problems,” including laws requiring that voters show identification before casting ballots and limiting early voting, which Mr. Obama said may appear neutral, but actually “have a disproportional effect on certain kinds of folks voting.”

“On the ground, there are still too many ways in which people are discouraged from voting,” said the president, who was joined by 160 civil rights leaders, activists and state and local officials who gathered at the White House to celebrate the law 50 years to the day after President Lyndon B. Johnson signed it.

His comments came a day after a federal appeals panel ruled that a strict voter identification law in Texas discriminated against blacks and Hispanics and violated the Voting Rights Act.

The case is regarded as an important marker for defining the reach of the law after a 2013 Supreme Court decision that struck down its most powerful enforcement tool — a requirement that states with histories of racial discrimination, including many in the South, win advance approval from the federal government before changing their election laws.

Attorney General Loretta E. Lynch said the Justice Department had “a number of investigations underway” into state practices that might violate the Voting Rights Act, but with the pre-clearance requirement of the law invalidated, the government’s ability to respond to problems had been hampered.

“With the loss of the pre-clearance remedy, we now are faced with a situation where we have to wade in once the damage is done,” Ms. Lynch said during a conference call organized by the White House. She said she was “tremendously gratified” with the Texas ruling, adding that she had not reviewed the state’s response.

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Representative John Lewis of Georgia said the struggle for the right to vote had not ended.Credit
Zach Gibson/The New York Times

The president’s remarks also came just as Republican presidential candidates were gathering in Cleveland for the first debate of the 2016 election, in which a dispute over voting rights could figure prominently. Democrats allied with Hillary Rodham Clinton have begun a nationwide legal battle to roll back Republican-enacted restrictions on voter access.

“Whoever I sit across from in the debates in the general election, I will be raising this,” Mrs. Clinton said Thursday in a radio interview with the Rev. Al Sharpton.

Mr. Obama, who in March went to Selma, Ala., to mark the 50th anniversary of a violent confrontation between the police and protesters that led to the passage of the voting rights measure, reiterated on Thursday the call he made there for Congress to pass an updated version.

But some influential Republicans have resisted a new version. On Thursday, Senator Mitch McConnell, Republican of Kentucky and the majority leader, said the law “has been a big success; it’s worked,” and suggested that a revision was not needed.

“It is also important to understand how different the South is now,” Mr. McConnell said, adding that there were more black elected officials in Mississippi than in any other state. “America’s come a long way, and the Voting Rights Act is intact, it was not struck down.”

Representative John Lewis, Democrat of Georgia, who was nearly beaten to death during the Selma march, said there was more to do.

“The struggle for the right to vote has been a long, hard, tedious struggle to redeem the soul of America,” Mr. Lewis said before introducing the president, “and the struggle is not over.”

Even as Mr. Obama called for tearing down the modern-day barriers that remain for minorities and others to cast ballots, he also said the biggest obstacle by far was citizens themselves. He proclaimed Sept. 22 National Voter Registration Day, a mass mobilization when groups including the N.A.A.C.P. will try to get as many people as possible to sign up to vote.

“Far more people disenfranchise themselves than any law does, by not participating, by not getting involved,” Mr. Obama said, noting that fewer than one-third of Americans participated in the 2014 midterm elections.

Amy Chozick contributed reporting from New York.

A version of this article appears in print on August 7, 2015, on Page A15 of the New York edition with the headline: Obama Urges Restoring Voting Rights Provisions. Order Reprints|Today's Paper|Subscribe